The invention relates to a deive for coupling pairs of optical fibers. Such a device includes two coupling members which are provided with fixing means for detachably connecting the coupling members to each other. Each coupling member is provided on one side with at least one circularly cylindrical recess. A bore extends from each recess as far as the other side of each coupling member for introducing, from the other side, an end of an optical fiber into the recess. A set of identical spherical balls, for centering the end of the optical fiber introduced into the recess, is provided in each recess.
Devices of this kind are used for coupling optical fibers in communication systems, where optical fibers are used for the transmission of light pulses carrying information. For the use and maintenance of the circuits used in such systems, mounting and removal of the devices should be easy. Considering the large numbers in which they are employed, the cost price of these devices should also remain within reasonable limits. Moreover, the devices have to be constructed so that each optical coupling between two optical fibers involves a minimal loss of energy.
A low-loss coupling requires the correct alignment of the axes of the fibers in the vicinity of the ends thereof where the coupling is realized, and also the correct positioning of the ends with respect to each other. The device described in the article "Triple-Ball Connector For Optical Fibres" by P. Hensel (published in "Electronics Letters," Vol. 13, No. 34, Nov. 24, 1977) represents an attractive solution for obtaining substantially the desired alignment and correct positioning. In the vicinity of the coupling location in the device, each fiber is fed through a calibrated opening of a cylinder whose diameter substantially equals the fiber diameter. The end of the fiber then enters a space which is enclosed by three mutually contacting identical balls, the centers of which form the apices of an equilateral triangle whose plane extends perpendicular to the axis of the enclosed fiber. When the diameter of the balls is suitably chosen, the space is dimensioned so that the diameter of the inscribed circle substantially equals the diameter of the fiber to be coupled.
In this device, the two fibers are coupled by bringing both sets of balls (each set being associated with one of the two fibers) into contact with each other so that each ball of each set is situated between two balls of the other set. The centers of the inscribed circles between the balls then coincide with the axes of the fibers. The foregoing can be realized only if the balls are arranged in a bush having a very accurately dimensioned inner diameter.